tldpropertiesllc vs. AT&T

I had AT&T combine billing up to Feb 2009 when I changed to a wireless business account and cancel the combine billing. I was paying by deduction from checking account and ask them to change to paper billing for the new business account. I later found that they never stop billing me on the combine home & wireless bill, but they had started the business wireless account billing for Feb 2009, double billing. I started calling them about the double billing in June 2011, I sent both bills and even talked to someone in the executive office. They told me I still owed a $250 balance, but I had paid we longer had the land line they were charging us for we even moved to another state. They stopped calling and responding after my contact, and I sent copies of both bills. I found out my sister was charged after she stopped the combined billing too. I have two years of the double bills, what can I do? Who do I contact now?
I think AT&T has used this as a way to double people, they tell you that the combine site can't see what the wireless site is doing, so they can't make changes to the other site, that is not acceptable for double billing!